The overall objective of this project is to determine the role of prostaglandins in the regulation of the circulation. For the current year the objectives were to investigate the influence of prostaglandin synthesis inhibitors on the peripheral vascular effects of ouabain, the interrelationships of the prostaglandin system and the renin angiotensin system, the effects of ACTH on the adrenal circulation and its dependence on prostaglandin synthesis, and the interrelationships of histamine and the prostaglandin system in the gastric circulation. The experimental preparation uses mongrel dogs and the prostaglandin measurements are made with gas chromatography-mass spectrometry techniques. In the coming year, the interrelationships of the prostaglandin system and the renin angiotensin system will be investigated further by focusing on the adrenergic receptor mechanisms of renin release and by attempting to measure the prostaglandin release coincident with renin release into the renal venous blood. The extrarenal circulatory effects of furosemide will be investigated and the interrelationship of histamine and the prostaglandin system will be pursued by using an isolated suspension of acid producing gastric cells.